The sail for a foiling International Moth is an interesting design challenge, somewhere between windsurfing and dinghy sailing. At Hyde we feel that foiling dinghies are at the cutting edge of the sport. Mike Lennon, Hyde's Technical Director has bought himself a boat and continues to work on the sail. The super lightweight new mainsail developed over the winter of 2009 is now available and has already proved fast on the racetrack.
In the flying shape include increasing depth and sleeve rotation in the lower half whilst doing the opposite in the upper half to allow the sail to wash out cleanly in the head. This set up allows more varying use off wind without stalling the upper sail.
The sail now feels more powerful downwind and is easier to de-power upwind.
The upper third can be now completely washed out with aggressive Cunningham use. This lowers the C of E and gives more righting moment in effect.
Outline shape has been modified to maximise luff and leech length - also following our competitors by lowering the effective luff under the lower band with aggressive “foot round". This increase in luff - and leech by extending the leech upwards, leads to a narrower sail with longer leading and trailing edges.
To increase control via Cunningham and vang we have changed material to the Hyde membrane system. By using a small yarn size we are able to use plenty of yarn passes where we think its needed whilst still getting a good cover in low stress areas without a weight penalty. The cover factor is important to ensure smooth transition from low to high stress areas. Due to the high fibre content the film content is reduced. The sail will close up on the leech with a very straight exit via the vang and will open and exhaust via the Cunningham.
The film is a polyester extruded sheet also known as Mylar or Dacron film. This is the same material as white woven Dacron sails are made from except they are drawn to filaments and woven. We are using Technora fibres with a thin film to lock the fibres in place.
This means very strong where its needed and not so where not needed - Thick film sails are the same strength in high and low load regions so by definition are over built or under built!
Hyde membrane system sails are smoother - stronger - lighter compared to panel sails offering similar stretch resistance.
The batten pockets are engineered to give similar resistance to stretch on both tacks - made from Technora laminate like the sail body. This makes the sail behave the same whichever tack you are on ! The battens are tapered in house to suit the sail mould design.
The cams have cupped ends where they meet the mast so don't fall off. All the battens carry cams to ensure smooth shape transition from tack to head.
Moth Mainsail 2C - Tri Radial ODL04 All round design
Moth Mainsail 2Dm - H-ms Membrane All round design
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